Microabrasive compositions containing oöids

ABSTRACT

Ooids, microabrasive compositions containing ooids and methods of making microabrasive compositions containing ooids are described. Generally, ooids represent small particles, which are selectable for size, size distribution, and other characteristics and can be used as a microabrasive particle. Ooids generally show a high level of symmetry, sphericity, roundness and a low aspect ratio. As described here, these characteristics generally yield a predictable and highly effective abrasive.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 62/463,030, entitled “Utility of Ooids and Other Carbonate SandGrains as Microabrasives” to Trower et al., filed Feb. 24, 2017, whichis incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention is directed to microabrasive compositions,including methods of making thereof. More particularly, the presentinvention is directed to microabrasives created from ooids withincreased homogeneity of size and shape.

BACKGROUND OF THE INVENTION

Plastic microbeads are small synthetic polymer particles, typicallysmaller than 1 mm in diameter, that were added to a variety of skin careproducts as gentle abrasive agents; they have also been used in avariety of household and industrial cleaning products. A number ofpolymers have been commonly added to skin care products, with the mostcommon being polyethylene. (See, e.g., Environment and Climate ChangeCanada, Microbeads—A Science Summary (July 2015); the disclosure ofwhich is incorporated herein by reference in its entirety.) Within thelast several years, there has been growing awareness and concern aboutthese synthetic microbeads as a significant source of microplasticpollution to terrestrial and marine ecosystems (do Sul and Costa,Enviro. Pollution (2014); Eriksen et al., Marine Pollution Bulletin(2013); Mason et al., Enviro. Pollution (2016); the disclosures of whichare hereby incorporated by reference in their entirety.) Recent andplanned legislation in the United States, Canada, and Europe has soughtto curtail and/or ban the use of microbeads in cosmetic products.(MacDonald, Environmental Defence Press Release, (Jun. 29, 2016); H.R.1321, 114th Cong. (2016); the disclosures of which are herebyincorporated by reference in their entirety.) Even prior to theseproposed and planned microbead bans taking effect, some companies havereplaced plastic abrasives with alternative particles, including walnutshells, silica gel beads, jojoba wax beads, and other waxes. Walnutshells are the subject of an ongoing lawsuit alleging that theangularity and roughness of this material causes “micro-tears” in skin.(Browning v. Unilever US, Inc., No. 8:2016cv02210 (C.D. Calif. FiledDec. 16, 2016); the disclosure of which is incorporated herein byreference in its entirety.) The low density and hydrophobicity of waxescan be problematic for even distribution within various cosmeticmaterials. While there has not been a comparable public demand for thebanning of microplastic abrasives in cleaning products, this too maychange and some of the non-plastic particles being used in skincareproducts (e.g., waxes and silica gel) are likely too soft to be usefulalternatives to plastic for these applications. There is, therefore, aclear need for a microabrasive material that is small, microscopicallysmooth, harder and denser than wax or amorphous silica, andenvironmentally benign.

SUMMARY OF THE INVENTION

In one embodiment, a microabrasive composition comprises a fluid matrixcontaining a plurality of ooids, where the ooids possess an average sizeof at least about 100 μm to less than about 650 μm; a size distribution,where at least 75% of the ooids range from about 75 μm to about 800 μm;an average roundness score of at least 0.4; and an average aspect ratioof less than 1.6.

In another embodiment, the ooids have an average size of about 115 μmand at least 75% of the ooids range from 90 μm to 140 μm.

In a further embodiment, the ooids have an average size of about 200 μmand at least 75% of the ooids range from 150 μm to 250 μm.

In yet another embodiment, the ooids have an average size of about 325μm and at least 75% of the ooids range from 240 μm to 450 μm.

In still another embodiment, the ooids have an average size of about 635μm and at least 75% of the ooids range from 480 μm to 800 μm.

In yet still another embodiment, the ooids have an aspect ratio of lessthan 1.5 and an average roundness of at least 0.5.

In yet a further embodiment, the ooids have an aspect ratio of less than1.4 and an average roundness of at least 0.7.

In still yet another embodiment, the ooids have an aspect ratio of lessthan 1.3 and an average roundness of at least 0.75.

In further still another embodiment, the fluid matrix is a personalhygiene product.

In another embodiment, a method for making a microabrasive compositioncomprising collecting a plurality of ooids from a source; selecting theplurality of ooids for an average size of at least about 100 μm to lessthan about 650 μm, a size distribution, where at least 75% of the ooidsrange from 75 μm to 800 μm, wherein the plurality of ooids afterselection possess an average roundness score of at least 0.4, and anaverage aspect ratio of less than 1.6; and combining the plurality ofooids with a fluid matrix.

In a further embodiment, the selecting step is performed using at leastone sieve.

In an additional embodiment, the ooids have an average size of about 115μm and at least 75% of the ooids range from 90 μm to 140 μm.

In a further embodiment, the ooids have an average size of about 200 μmand at least 75% of the ooids range from 150 μm to 250 μm.

In yet another embodiment, the ooids have an average size of about 325μm and at least 75% of the ooids range from 240 μm to 450 μm.

In still another embodiment, the ooids have an average size of about 635μm and at least 75% of the ooids range from 480 μm to 800 μm.

In yet still another embodiment, the ooids have an aspect ratio of lessthan 1.5 and an average roundness of at least 0.5.

In yet a further embodiment, the ooids have an aspect ratio of less than1.4 and an average roundness of at least 0.7.

In still yet another embodiment, the ooids have an aspect ratio of lessthan 1.3 and an average roundness of at least 0.75.

In further still another embodiment, the fluid matrix is a personalhygiene product.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings where:

FIG. 1 shows scanning electron microscope images of variousmicroabrasive particles including ooids, in accordance with variousembodiments of the invention. In this figure, the scale bar equals 100μm.

FIG. 2 illustrates the size distribution of various microabrasiveparticles, including ooids, in accordance with various embodiments ofthe invention.

FIG. 3 shows scatter plots describing symmetry, sphericity, aspectratio, and roundness of various microabrasive particles, includingooids, in accordance with various embodiments of the invention.

FIG. 4 illustrates a multidimensional analysis of symmetry, sphericity,aspect ratio, and roundness, including a principal components analysis(Panel A) and a scatter plot of aspect ratio versus roundness (Panel B)for various microabrasive particles, including ooids, in accordance withvarious embodiments of the invention.

FIG. 5 illustrates the dissolution rate of ooids of various sizes as afunction of saturation state, in accordance with various embodiments ofthe invention.

FIG. 6 shows scanning electron microscope images of ooids showing thestability of ooids over time, in accordance with various embodiments ofthe invention.

FIG. 7 depicts a bar graph showing the abrasion rates of variousmicroabrasive particles, including ooids, in accordance with variousembodiments of the invention.

FIG. 8 illustrates a process for making a microabrasive composition, inaccordance with various embodiments of the invention.

DETAILED DESCRIPTION

Turning now to the diagrams and figures, embodiments of the inventionare generally directed to ooids, microabrasive compositions containingooids and methods of making microabrasive compositions containing ooids.Generally, ooids represent small particles, which are selectable forsize and size distribution. Also ooids generally show a high level ofsymmetry, sphericity, roundness and a low aspect ratio. Thesecharacteristics generally yield a predictable and highly effectiveabrasive, which can roll and not snag during abrasion, which avoidsmicro-tears of skin tissue. It should be noted that ooids are also knownas oöids. Uses herein of the words ooid, ooids, or oolitic are intendedto also reflect and encompass oöid, oöids, and oölitic.

Ooids are a type of well-rounded, well-sorted sand that occur naturallyin tropical shallow marine environments and certain lacustrineenvironments. These sand particles are made of calcium carbonate(CaCO₃). Together with other carbonate sand (including abraded androunded shell fragments), ooids are an ideal natural microbeadalternative based on their shape, size, surface texture, chemistry,density, and hardness. Ooids and other carbonate sands can be sourcedfrom tropical marine sands and represent a regenerative resource. Afteruse and during their disposal, all wastewater reactions involving theseparticles constitute a net carbon sink, opposed to plastic- andwax-based particles.

Non-oolitic carbonate sands are typically composed of shell and otherskeletal fragments. These materials also naturally occur in similarsizes to microplastic abrasives, but have more angular shapes and moreirregular surface textures if those properties are desirable for aparticular application. Both ooids and other carbonate sands arecommonly composed of aragonite, though some are composed of calcite orcontain mixtures of both CaCO₃ polymorphs. The hardness of calcite andaragonite fall in the range of 3-4 on the Mohs hardness scale, somewhathigher halite (NaCl, table salt, 2-2.5 Mohs hardness), which is alsoused as an abrasive in some skincare products. However, unlike angularcubic halite crystals, carbonate sands, and ooids in particular, tend tobe much more rounded and therefore their increased hardness can beoffset by their smoother surface textures. The densities of calcite andaragonite, including ooids range from 2.7-2.9 g/cm³, somewhat higherthan the density of halite (2.1 g/cm³), but much higher than the densityof jojoba wax (0.9 g/cm³) or silica gels (0.7-2.2 g/cm³, depending onporosity), whose lighter-than-water density makes even distributionwithin a variety of skincare products problematic.

Ooids and other carbonate sand can be sourced from natural environmentsand are a regenerative resource: ooids are formed as a consequence ofshallow marine waters that are supersaturated with respect to CaCO₃ andother carbonate sands form via the physical breakdown and abrasion ofshell material in high energy beach and shoal environments. At ooidgrowth rates anticipated from field and empirical constraints andobserved in recent experiments, ooid-forming environments seeded withappropriate nuclei have the potential to regenerate sand-sized ooids onthe order of under one to several years under optimal current velocitiesand sediment transport patterns. (Trower et al., Earth and PlanetaryScience Letters (2017), the disclosure of which is herein incorporatedby reference in its entirety.) Preliminary experimental results indicatethat ooids are shelf-stable in a variety of commercially available faceand body wash products over timescales at least one year. Ooids andother carbonate sands are also natural pH buffers, which wouldcontribute to their long term stability in cosmetic products.

Atmospheric carbon dioxide (CO₂)—a known greenhouse gas—absorbs asubstantial fraction of outgoing infrared radiation and contributes thepredominant increase in radiative forcing—and consequently globaltemperature change—due to anthropogenic emissions. In contrast withplastic microabrasives, using natural ooids or other carbonate sands asmicroabrasive materials engenders a net carbon sink of CO₂ from theatmosphere. Thus from the perspective of the global carbon cycle, ooidscan represent a “green” or at least “greener” consumer alternative toplastic microabrasives.

Carbonate ooids composed of either aragonite or calcite are inert in orcan undergo relatively rapid dissolution in solutions under-saturatedwith respect to these phases primarily due to low relative abundances ofcalcium (Ca²⁺) and carbonate (CO₃ ²⁻) ions. As such, ooids require nospecial remediation. The dissolution in water includes all municipalwastewater and nearly all natural non-marine surface, soil andgroundwater. The dissolution process produces two molar equivalents ofcarbonate alkalinity for every one mole of solid carbonate derived fromooids. The dissolution process constitutes a sink of CO₂ from theatmosphere, as shown in Equation 1:CaCO_(3(s))+H₂O+CO₂→Ca₂ ₊ _((aq))+2HCO₃ ⁻ _((aq))  (1)

Ooids harvested from marine or lacustrine environments constitute anatural source of solid CaCO₃ and thus represent a straightforwardremoval of atmospheric CO₂ during their subsequent dissolution post use.The use of ooids combats two sources of pollution and/or environmentalimpact: reducing the carbon footprint associated with the use ofproducts containing plastic or polymeric microbeads and counteringanthropogenic CO₂, which is the leading force associated with climatechange. With the production of carbonate, ooid use can also act as a pHbuffer against corrosion and leaching of unwanted chemicals, includinglead, in household or industrial plumbing as well as wastewater systems.Additionally, ooids would not contribute to additional scaling orprecipitation in “hardwater” districts. Hardwater districts are waterdistricts in which the water is already saturated with carbonate. Thecarbonate-saturated water prevents additional addition of carbonate tothe water from carbonate-based ooids. Furthermore, any escape ofcarbonate minerals to the marine system would not pose detrimentalenvironmental effects as they are common sedimentary materials and wouldact as buffers against ocean acidification.

Although plastic microbeads in cosmetic products have garnered the mostpopular and media attention recently, their use as microabrasivesextends to cleaning products and other materials. A significant problemwith plastic microabrasives is that they can pollute the environment.The advantage of ooids and other carbonate sand is as a “greener”alternative to conventional microbeads. However, natural ooids possess awide-range of sizes, size distributions, and other characteristics(e.g., roundness and sphericity) that may not be beneficial for use asmicroabrasive particles; thus understanding which specificcharacteristics make ooids advantageous and selecting ooids for thesecharacteristics provides microabrasive particles that are anadvantageous alternative to other microabrasive particles. Additionallythe use of ooids is not limited to cosmetic products—ooids can be usedfor any microabrasive application. The more widely adopted carbonateooid microabrasives are, the greater their positive impact on the carboncycle by reducing CO₂, a known greenhouse gas, particularly incomparison with microplastics.

Ooid Characterization

Ooids naturally exist in numerous shapes, sizes, size distributions, andother physical characteristics, depending on where they are sourced andhow they are formed. For use as a microabrasive particle, certain sizes,shapes, or other characteristics may be more beneficial depending on thespecific use. Embodiments of the present invention are directed to ooidsselected specific sizes, size distributions, and other physicalcharacteristics discussed below, which make these selected ooidsadvantageous for use as a microabrasive particle.

Turning now to FIG. 1, typical ooids (Panel D) are 0.25-0.6 mm (250-600μm) in diameter, well within the range of plastic microbeads harvestedfrom a commercial face wash (Panel A), plastic microbeads harvested froma commercial body wash (Panel B), and crushed walnut shells harvestedfrom a commercial body wash (Panel C). In this figure, the scale barsare equal 100 μm. As seen in Panel D, ooid surfaces are microscopicallysmooth due to natural polishing by abrasion in the environments in whichthey occur. This smooth surface differs from the other microabrasiveparticles, which exhibit coarse surfaces (Panels A and C) or knobbysurfaces (Panel B). Additionally, ooids are relatively spherical,well-rounded grains, which is similar to some plastic microbeads (PanelsA and B), and ooids are notably and significantly less angular thanwalnut shell fragments (Panel C). Thus, ooids of some embodimentsexhibit different physical characteristics, which may provide anadvantage over other microabrasive particles.

Turning to FIG. 2, the data plots illustrate sizes and sizedistributions of walnut shells, and plastic or polymeric microabrasiveparticles harvested from various personal hygiene products (e.g., facewashes and body washes) in addition to ooids of some embodiments of theinvention. As illustrated in FIG. 2, ooids of numerous embodimentsdemonstrate similar sizes to plastic microbeads and other microabrasiveparticles. Specifically, Panel A illustrates histograms of the sizeranges of samples various types of microabrasive particle, includingplastic microbeads harvested from commercial face washes, plasticmicrobeads harvested from a commercial body washes, ooids in accordancewith various embodiments, other forms of carbonate sand, and crushedwalnut shells. Panel B graphs size ranges and standard deviation of thevarious types of microabrasive particles. The upper plot in Panel Billustrates the size distribution as a whisker plot, where the mediansize, or fiftieth percentile (D₅₀), for each sample is plotted as thecentral point, as represented by a square, diamond, circle, star ortriangle for each type of microabrasive particle as denoted in thelegend at the bottom of Panel B. The upper whisker ends at the pointthat represents the ninetieth percentile (D₉₀) in the distribution ofthe microabrasive particles, while the lower whisker ends at the pointthat represents the tenth percentile (D₁₀) in the distribution of themicroabrasive particles. The lower graph in Panel B plots the standarddeviation of each sample of microabrasive particles.

As shown by the graphs in FIG. 2, ooids of various embodiments may beselected for average sizes ranging from about 100 μm up to about 650 μm.In some embodiments, the average size may be approximately 100 μm,approximately 200 μm, approximately 300 μm, approximately 325 μm,approximately 400 μm, approximately 425 μm, approximately 450,approximately 500 μm, approximately 550 μm, approximately 600 μm, orapproximately 650 μm. Further, ooids may be selected for a sizedistribution where at least 70%, at least 75%, or at least 80% of theooids exist in a range from about 75 μm to about 800 μm. In someembodiments, the range may be approximately 90 μm to approximately 140μm, approximately 150 μm to approximately 250 μm, approximately 165 μmto approximately 250 μm, approximately 240 μm to approximately 420 μm,approximately 250 μm to approximately 460 μm, approximately 325 μm toapproximately 550 μm, approximately 340 μm to approximately 500 μm,approximately 370 μm to approximately 600 μm, approximately 400 μm toapproximately 800 μm, or approximately 490 μm to approximately 700 μm.

As illustrated in FIG. 2, the selection of ooids in various embodimentsplaces these particles within the range of other microabrasive particlesrather than a natural distribution of ooid sizes. Additionally, as shownin FIG. 2, ooids of some embodiments may demonstrate a smaller sizedistribution and lower standard deviation when compared to othermicroabrasive particles, indicating that the selection of ooids invarious embodiments produces microabrasive particles, which arecomparable in size to currently used microabrasive products and providea narrower distribution than would otherwise be available from naturalooids. Further, additional physical characteristics of ooids, such asroundness, aspect ratio, and additional physical characteristicsdiscussed below, may make ooids of certain embodiments an advantageousalternative to other microabrasive particles.

Turning now to FIG. 3, various physical characteristics ofmicroabrasives in accordance with embodiments are illustrated.Specifically, FIG. 3 illustrates mean symmetry (Panel A), meansphericity (Panel B), mean aspect ratio (Panel C), and mean roundness(Panel D). Symmetry is a measure of how much symmetry individualparticles exhibit and is scored on a scale of 0 (no symmetry) to 1(perfect symmetry). Sphericity is a three-dimensional measurement of thedivergence of a shape from a perfect sphere. Sphericity is calculated as4πA/P², where P is the perimeter and A is the area of the particleprojection. A perfect sphere has a sphericity of unity (scored as a 1 onthe scale), while other shapes have a sphericity index of less than 1.Aspect ratio is the ratio of the long axis to the short axis ofmeasurements taken of individual particles from two axes (e.g., lengthand width). An aspect ratio of 1 means that the two axes are equal, andincreasing scores indicates that the two axes are less similar.Roundness is a two-dimensional measurement of the roundness ofindividual particles using the Wadell Roundness Index. (Wadell, J. ofGeology (1932), the disclosure of which is herein incorporated byreference in its entirety). The Wadell Roundness Index is calculated asΣr_(i)/(nR), where r_(i) are the radii of curvature of particles'corners, R is the radius of the largest inscribed circle and n is thenumber of particle corners measured. A score of 1 represents perfectlyround particles.

As shown in FIG. 3, ooids of some embodiments may possess greater levelsof symmetry (Panel A), sphericity (Panel B), and roundness (Panel C)than other forms of microabrasives. Additionally, ooids of certainembodiments may also possess lower aspect ratios than other forms ofmicroabrasives. Specifically, ooids of various embodiments may possess ahigher level of symmetry when compared to other microabrasives, wherethe symmetry of ooids generally ranges from about 0.87 to about 0.95,such that the mean symmetry of ooids of various embodiments may be atleast 0.87, at least 0.88, at least 0.89, at least 0.90, at least 0.91,at least 0.92, at least 0.93, or at least 0.94. Additionally, ooids ofsome embodiments may possess higher levels of sphericity, when comparedto other microabrasives, where sphericity of ooids generally ranges fromabout 0.80 to about 0.95, such that the mean sphericity of ooids of someembodiments may be at least 0.81, at least 0.83, at least 0.87, at least0.88, at least 0.89, at least 0.90, at least 0.91, at least 0.92, or atleast 0.93. Further, while other microabrasive particles may exhibitaspect ratios of close to 2, ooids of may possess aspect ratios of lessthan 1.6, such that ooids of numerous embodiments possess aspect ratiosof less than 1.6, less than 1.55, less than 1.5, less than 1.45, lessthan 1.4, less than 1.35, less than 1.3, or less than 1.25. Ooids ofmany embodiments also may possess higher roundness than othermicroabrasives, where roundness of ooids generally ranges from about0.45 to 0.79, such that the roundness of ooids of some embodiments havemay be at least 0.45, at least 0.50, at least 0.55, at least 0.60, atleast 0.65, at least 0.69, at least 0.70, at least 0.71, at least 0.72,at least 0.73, at least 0.74, at least 0.75, at least 0.76, at least0.77, or at least 0.78. Thus, ooids selected according to variousembodiments show advantageous characteristics in terms of symmetry,sphericity, aspect ratio, and roundness, which do not exist in currentlyused microabrasive particles and may not exist in naturally occurringooids.

Turning now to FIG. 4, a principal components analysis of roundness,aspect ratio, symmetry, and sphericity of various microabrasiveparticles is plotted in Panel A, while a plot of aspect ratio versusroundness for various microabrasive particles is plotted in Panel B. InPanel A, the principal components analysis shows the vectors forroundness and aspect ratio are nearly perfectly orthogonal, andtogether, these physical characteristics provide the most useful metricsof microabrasive particle shape. Panel B illustrates the aspect ratioand roundness of various samples of various microabrasive particles. Inparticular, ooids of various embodiments may form a cluster showing ahigh level of roundness and low aspect ratio, whereas other carbonatesands and microabrasives harvested from body washes do not formclusters. Additionally, although microabrasives harvested from facewashes form a cluster, the cluster does not show a degree of roundnessexhibited by ooids of several embodiments. Thus, ooids of certainembodiments may be selected for specific, correlative characteristics,which may not otherwise exist in all ooids from all environments.

Turning now to FIG. 5, a graph of the dissolution rates of ooids ofcertain embodiments is plotted. Carbon dioxide (CO₂) in the atmosphereabsorbs a substantial fraction of outgoing infrared radiation andcontributes the predominant increase in radiative forcing—andconsequently global temperature change—due to anthropogenic emissions.In contrast with plastic microabrasives, using either synthetic ornatural ooids as microabrasive materials engenders either a net carbonsource or net carbon sink, respectively, of CO₂ from the atmospheredepending on the processes and mechanisms of their synthesis. Thus fromthe perspective of the global carbon cycle, ooids can represent a“green” or at least “greener” consumer alternative to plasticmicroabrasives.

FIG. 5 specifically illustrates the dissolution rate for various sizesof carbonate (CaCO₃) ooids as a function of the saturation state (Ω) ofhousehold and natural waters. Carbonate ooids composed of eitheraragonite or calcite undergo relatively rapid dissolution in solutionsunder-saturated with respect to these phases primarily due to lowrelative abundances of carbonate ion (CO₃ ²⁻). This includes allmunicipal wastewater and nearly all natural non-marine surface, soil andgroundwater. The dissolution process produces two molar equivalents ofcarbonate alkalinity for every one mole of solid carbonate derived fromooids. This process constitutes a sink of CO₂ from the atmosphere (Eq.1).CaCO_(3(s))+H₂O+CO₂→Ca₂ ₊ _((aq))+2HCO₃ ⁻ _((aq))  (1)Ooids harvested from marine or lacustrine environments constitute anatural source of solid CaCO₃ and thus represent a straightforwardremoval of atmospheric CO₂ during their subsequent dissolution post-use.

The dissolution behavior of grains in natural (drinking, household,gray, and waste) water is described by a Saturation State (Ω)—commonlyused measure in geochemistry of the thermodynamic driving force to theequilibrium state. Omega is typically defined as written in Equation 2:Ω=[Ca²⁺][CO₃ ²⁻]/K_(s)  (2)

-   -   where:        -   [Ca₂ ⁺] and [CO₃ ²⁺] denote chemical activities, and        -   K_(s) reflects the solubility constant.            A related quantity used in hydrology and engineering is the            Saturation Index (SI), which is the log of the saturate            state (Ω). For drinking water, the SI for calcium carbonate            is commonly called the Langelier Saturation Index (LSI).            (Langelier, J. of Amer. Water Works Assoc. (1936), the            disclosure of which is hereby incorporated by reference in            its entirety). The parameter SI is a dimensionless measure            of the tendency for the water to dissolve or precipitate            carbonate. It is computed as the difference between the            measured pH of the water and the pH at calcite saturation            (pH_(s)). Negative LSI values dissolve carbonate, while            positive LSI values will lead to precipitation of carbonate.            The rate of dissolution varies as a function of the            deviation from equilibrium. Typical municipal water            facilities try to maintain LSI near 0 to avoid strongly            corrosive or strongly scaling waters. For well waters the            LSI tends to be negative. The USGS has produced large            compilations of measurements of LSI from a range of drinking            waters sourced. (See Belitz et al., US Geological Survey            Scientific Investigations Report 2016-5092 (2016), the            disclosure of which is hereby incorporated by reference in            its entirety.) According to these exhaustive measurements,            the average LSI for well water across the fifty states and            the District of Columbia is approximately −0.96. Ooids of            some embodiments, which may be present in these waters may            help buffer the LSI, and in cases where systems might be            corrosive they help raise the LSI via dissolution. Thus,            ooids of certain embodiments may be selected based on            chemical composition factors that affect dissolution and            buffering capacity, which may not be present in ooids            comprised of other elements or present in some environments.

Turning now to FIG. 6, scanning electron microscope images demonstratestability of ooids of various embodiments at 0 months, 6 months, and 13months (scale bars=100 μm). Ooids of some embodiments may be used inconjunction with a detergent based matrix. Such a matrix could be apersonal hygiene product like a face wash, body wash, or any otherproduct that may be used for personal hygiene. Additionally, such amatrix may be an industrial product, which may benefit from the additionof a microabrasive, such as an industrial scrub, polish, liquidsandpaper, or any other industrial product that may benefit from amicroabrasive. FIG. 6 demonstrates that ooids of numerous embodimentsmay remain stable in a commercial body wash for at least one year. Theability to be stable in fluid matrices, which may include detergents,stabilizers, or other components may not be present in all ooids. Thus,ooids of some embodiments may be selected for the ability to remainstable in specific fluid matrices.

Ooids of several embodiments may also be selected for a degree ofstickiness. Some microabrasives, such as microabrasives generated fromwaxes, such as jojoba wax, or plastics and/or polymers may possesscharacteristics that allow or encourage the microabrasive particles tostick or clump together into larger amalgamations comprising a pluralityof individual microabrasive particles. Such clumping or sticking mayreduce the efficacy of a composition to work as effectively as amicroabrasive, as the number of individual particles will be reduced inthe composition. Additionally, clumping or sticking may also reduce theroundness, sphericity, and symmetry in addition to increasing the aspectratio. These factors may also affect the efficacy of a microabrasivecomposition, thus sticking and/or clumping may reduce the overallefficacy of a microabrasive composition. Factors that may affectsticking and/or clumping could be heat, humidity, pressure, storagetime, stability of the microabrasive particles, certain chemicalcomponents in a matrix of a microabrasive composition, and/or any otherfactor that may lead to individual microabrasive particles stickingand/or clumping together.

Ooids of various embodiments may also be selected for deformabilitycharacteristics. Some microabrasive particles may exhibit the ability todeform, or alter shape, under certain circumstances. A desired and/orefficacious shape may be round and/or spherical microabrasive particles,where these microabrasive particles may exhibit the ability to rollacross a surface rather than drag. Additionally, microabrasive particlesused in personal hygiene products that drag across a surface may causedamage to a person's skin (e.g., walnut shells). Thus, a change of shapeaway from round and/or spherical may reduce the efficacy of theparticles to act in its desired capacity as a microabrasive.Microabrasive particles manufactured from waxes, plastics, polymersand/or other materials may be susceptible to deforming under certaincircumstances, such as heat, pressure, time, chemical reactions, and/orany other factor that may have an effect on the material composition ofan individual microabrasive particle.

Ooids of certain embodiments may possess smooth surfaces. A smoothsurface may be beneficial to certain microabrasive particles, in that asmooth surface may allow a microabrasive particle to slide, glide,and/or roll across a surface. A smooth surface may be desirable inooids, as the surfaces of some microabrasive particles, such as walnutshells and plastic or polymeric microabrasive particles, may not besmooth. As such, some microabrasive particles, may exhibit dimples,crevices, protrusions, crags, roughness, and/or any other characteristicthat differs from smooth. Such external features of a microabrasiveparticle may cause damage to a surface by dragging, pulling, gouging,scraping, tearing, and/or any other damaging action across a surface.Not all ooids may exist the same level of smoothness, which may provideadvantages over a rough or coarse surface. Thus, selecting ooids forsurface smoothness may be desirable or beneficial for some uses.

Quality of Ooids as an Abrasive

Turning now to FIG. 7, ooids show similar rates of abrasion as othermicroabrasive particles. Specifically, FIG. 7 illustrates the abrasionrate (mm/hr) of ooids of various embodiments versus a commercially usedmicroabrasive particle (listed as “Microbeads”) and a smooth surface.The assay indicates that ooids of some embodiments exhibit a slightlyhigher rate of abrasion when compared to commercially used microabrasiveparticles. The method of performing the assay will be described below.

Uses of Ooids

Some embodiments may be microabrasive compositions containing ooids.

Microabrasive compositions of certain embodiments may contain ooidsalong with a fluid matrix. The fluid matrix may be gaseous or liquid andmay consist of lotions, detergents, pH buffers, nutrients, minerals,stabilizers, and/or any other compound that may be beneficial for aparticular use in a microabrasive composition. Microabrasivecompositions of various embodiments may be a personal hygiene product,such as face wash, body wash, and/or any other type personal hygieneproduct. Alternatively, microabrasive compositions of some embodimentsmay be an industrial product, such as a scrub, polish, liquid sandpaper,or any other industrial product that may include microabrasiveparticles.

Methods of Making a Microabrasive Composition

Turning now to FIG. 8, some embodiments include a method of making amicroabrasive composition. This method (800) may include collecting aplurality of ooids from a source (810). As described above, ooids mayarise in aquatic environments and show varying characteristics based onthe source location. Such sources may include bodies of water, includinglakes, oceans, seas, coves, tributaries, gulfs, and/or any other sourcewhere ooids are present. Additionally, ooids from a combination ofsources may be collected in instances where a variety of sources may bebeneficial. However, different sources may produce ooids which do notexhibit the advantageous physical characteristics described herein(e.g., roundness and aspect ratio). Thus, identifying sources whichproduce ooids with the desired, advantageous characteristics may bebeneficial for collecting ooids in accordance with various embodiments.

Collected ooids may further be selected for a variety of characteristics(812), including size, size distribution, roundness, symmetry,sphericity, aspect ratio, degree of smoothness, degree of abrasiveness,degree of dissolution, degree of stability, and/or any other factor thatmay be beneficial or desired for use of the ooids. Additionally, subsetsof collected ooids may be selected for differing characteristics. Theselection of the collected ooids may occur by using a filter, sieve,mesh, grating, and/or any other system that allows for the exclusion ofcertain characteristics. Further, ooids of various embodiments may beselected solely for some features, where the resulting ooids afterselection possess additional desirable characteristics. For example, theselection process (812) may select for size and/or size distribution,and the selected ooids possess a desired roundness, aspect ratio,sphericity, and/or symmetry.

The selected ooids may then be combined with a matrix (814). The matrixmay be fluid or solid, such that the ooids may be affixed to a solidsurface, such as a sandpaper, rasp, plane, and/or any other solidsurface used for microabrasion. Additionally, the matrix may be gaseousor liquid. Additionally, a fluid matrix may be of any viscosity orcomposition for its intended purpose. Further, a fluid matrix mayconsist of lotions, detergents, pH buffers, nutrients, minerals,stabilizers, and/or any other compound that may be beneficial for aparticular purpose in a microabrasive composition. Such purposes mayinclude as a personal hygiene product or an industrial product. Personalhygiene products may be a face wash, body wash, and/or any personalhygiene product, while industrial products may be a scrub, polish,liquid sandpaper, or any other industrial product that may includemicroabrasive particles.

EXAMPLES

Characterizing Commercially Used Microabrasive Particles

Commercially used microabrasive particles were harvested fromcommercially purchased personal hygiene products. These products werefiltered to collect microabrasive particles. The collectedmicroabrasives were washed with water and allowed to dry.

Microabrasive particles harvested from commercially available productswere observed using dynamic image analysis as well as light and scanningelectron microscopy. Particle size and shape characteristics, includingsymmetry, sphericity, aspect ratio, and roundness, were determined usinga Retsch Camsizer P4.

Collecting Ooids

Ooids were collected from various locations known for producing ooids,including Turks and Caicos, and Bahama islands and cays, and associatedchannels and shoals associated with these locations. Ooids wereoptionally selected for specific sizes using sieves with pores toexclude the passing of various sizes. Collected ooids were then observedusing dynamic image analysis as well as light and scanning electronmicroscopy. Particle size and shape characteristics, including symmetry,sphericity, aspect ratio, and roundness, were determined using a RetschCamsizer P4.

Measuring Abrasion of Microabrasive Particles

Abrasion experiments were performed by comparing ooids to commerciallyharvested microabrasive particles; the results of which are illustratedin FIG. 7. Specifically, “microbeads” were harvested from Neutrogena®Face Scrub. Low tensile strength polyurethane foam (σT=0.32 MPa) wasused as the medium being abraded. Abrasion chambers were constructed bysecuring a 3.5 cm thick foam disc to the base of a 200 mL beaker, 6.5 cmin diameter. The microabrasive particles being tested were immobilizedas a monolayer across a flat surface 4 cm in diameter. The abrasivesurfaces were weighted to 80 g, placed in the abrasion chambers, andsubmerged in water. To insure that any measured abrasion was not merelydue to weight, a control was conducted using an identically weightedsurface but without any abrasive material (smooth surface). The chamberswere sealed with parafilm and shaken at 230 rpm for 1-3 hours. Abrasionwas measured as depth scoured in the foam discs by the weightedsurfaces. Rates reported here are averages of triplicates, error barsrepresent standard error between triplicates.

DOCTRINE OF EQUIVALENTS

While the above description contains many specific embodiments of theinvention, these should not be construed as limitations on the scope ofthe invention, but rather as an example of one embodiment thereof.Accordingly, the scope of the invention should be determined not by theembodiments illustrated, but by the appended claims and theirequivalents.

What is claimed is:
 1. A personal hygiene product formulationcomprising: a fluid matrix containing a plurality of ooids and at leastone of the group consisting of a detergent, a lotion, a pH buffer, anutrient, a mineral, and a stabilizer; wherein the ooids: possess anaverage size of at least about 100 μm to less than about 650 μm; possessa size distribution, where at least 75% of the ooids range from about 75μm to about 800 μm; possess an average roundness score of at least 0.4;and possess an average aspect ratio of less than 1.6.
 2. The personalhygiene product formulation of claim 1, wherein the detergent basedmatrix is a body wash.
 3. The personal hygiene product formulation ofclaim 1, wherein the detergent based matrix is a face wash.
 4. Thepersonal hygiene product formulation of claim 1, wherein the ooids havean average size of about 115 μm and at least 75% of the ooids range from90 μm to 140 μm.
 5. The personal hygiene product formulation of claim 1,wherein the ooids have an average size of about 200 μm and at least 75%of the ooids range from 150 μm to 250 μm.
 6. The personal hygieneproduct formulation of claim 1, wherein the ooids have an average sizeof about 325 μm and at least 75% of the ooids range from 240 μm to 450μm.
 7. The personal hygiene product formulation of claim 1, wherein theooids have an average size of about 635 μm and at least 75% of the ooidsrange from 480 μm to 800 μm.
 8. The personal hygiene product formulationof claim 1, wherein the ooids have an aspect ratio of less than 1.5 andan average roundness of at least 0.5.
 9. The personal hygiene productformulation of claim 1, wherein the ooids have an aspect ratio of lessthan 1.4 and an average roundness of at least 0.7.
 10. The personalhygiene product formulation of claim 1, wherein the ooids have an aspectratio of less than 1.3 and an average roundness of at least 0.75.